Method for manufacturing die and molding obtained therewith

ABSTRACT

A substrate  11  is patterned by photolithography to make a first original plate. Next, the pattern  11   a  of the first original plate is transferred to make a second original plate  12 . Next, the second original plate  12  is machined to make a die. Further, the pattern  12   b  of the second original plate  12  is transferred to make a third original plate  13 , which is used as a die. This provides a method for manufacturing a die by which a special shape, for example, a shape having a high aspect ratio portion can be easily formed and a molding obtained therewith.

CROSS REFERENCE TO RELATED APPLICATION

This is a continuation of International Application No.PCT/JP2006/310726, filed May 30, 2006, which is incorporated herein byreference in its entirety.

TECHNICAL FIELD

The present invention relates to a method for manufacturing a die and amolding obtained therewith, and more specifically, it relates to amethod for manufacturing a die using photolithography and machining anda molding obtained therewith.

BACKGROUND ART

With recent reduction in size, thickness, and weight of electronics, itis hoped that special shapes, for example, a shape having a high aspectratio portion will be realized. Specifically, formation of, for example,a deep groove having an arbitrarily shaped protrusion in the bottomthereof is hoped. It is obvious that electronics will be further reducedin size, thickness, and weight, and it is expected that the demands forthese special shapes will increase further. In anticipation of thesedemands, approaches to realizing the above special shapes, for example,fabrication of a fine structure by photolithography using X-ray andaccuracy improvement in machining, are increasingly active.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

However, when the above special shapes are formed by machining, thecutting tool size of processing machine is a problem. It is difficult toprocess a pattern less than 100 μm in width. In addition, it isdifficult to process, by machining, what has an aspect ratio of one ormore on the order of magnitude of micrometers. On the other hand, whenthe above special shapes are formed by photolithography, the processingaccuracy in the depth direction can vary about several percent. Inaddition, photolithography is disadvantageous in that thecontrollability in processing an arbitrary shape such as a tapered shapeor a curved shape is poor.

The present invention is made in consideration of such points, and anobject of the present invention is to provide a method for manufacturinga die by which a special shape, for example, a shape having a highaspect ratio portion can be easily formed, and a molding obtainedtherewith.

Means for Solving the Problems

In an aspect of the present invention, a method for manufacturing a dieincludes the steps of patterning a substrate by photolithography to makea first original plate, transferring the pattern of the first originalplate to make a second original plate, and machining the second originalplate to make a die.

According to this method, photolithography is used for forming, forexample, a high aspect ratio portion in a fine structure, and machiningis used for processing an arbitrary shape in the fine structure with ahigh degree of accuracy. Therefore, a special shape, for example, ashape having a high aspect ratio portion can be easily formed.

In another aspect of the present invention, a method for manufacturing adie includes the steps of forming a depression in a substrate to make afirst original plate, transferring the pattern of the first originalplate to make a second original plate having a protrusion correspondingto the depression, and machining the protrusion of the second originalplate to make a die.

According to this method, the protrusion of the second original platecorresponding to the depression of the first original plate is machined.Therefore, this method makes possible complex microfabrication of a sidesurface or a bottom surface in a fine depression smaller than the sizeof the cutting tool in machining.

The method for manufacturing a die of the present invention preferablyincludes the step of transferring the pattern that the die has to make athird original plate, and it is preferable that the third original platebe used as a die or a mother die of a die. According to this method,using the third original plate as a mother die makes it possible toobtain a die with which, for example, a stripe groove or a finedepression or protrusion can be formed, to an accuracy of machining, ina tapered surface or a bottom surface of a fine structure that cannot beprocessed by machining, for example, a fine structure smaller than thesize of the cutting tool used for machining. As a result, it is possibleto significantly expand the limit of die processing.

A molding of the present invention is molded using the above die or adie obtained using the above mother die. The molding of the presentinvention preferably includes a relatively high aspect ratio portion.

Advantages

According to the method of the present invention, a depression is formedin a substrate to make a first original plate, the pattern of the firstoriginal plate is transferred to make a second original plate having aprotrusion corresponding to the depression, and the protrusion of thesecond original plate is machined to make a die. Therefore, a specialshape, for example, a shape having a high aspect ratio portion can beeasily formed, and a fine depression or protrusion can be easily formedby machining with a high degree of accuracy in a tapered surface or abottom surface of a fine structure smaller than the size of the cuttingtool for machining.

BEST MODE FOR CARRYING OUT THE INVENTION

Photolithography and machining have advantages and disadvantages. Thatis, photolithography is advantageous to processing a micropattern or alarge area at once and to processing a special shape. Currently, amicropattern of several tens of nanometers in width can be formed. Inaddition, photolithography enables one to process a large range at onceand to form a special shape in which the same portion needs to beprocessed more than once, for example, a grating shape, and a shapehaving an aspect ratio of more than 10. On the other hand, machining isadvantageous to processing with high dimensional accuracy and toprocessing with small surface roughness. Machining enables processingwith very small dimensional variation.

The inventors focused attention on the above-described points, foundthat a special shape, for example, a shape having a high aspect ratioportion could be easily formed by fusing the fine patterning byphotolithography and the high-accuracy processing by machining andthereby compensating for the disadvantage of photolithography withmachining and compensating for the disadvantage of machining withphotolithography, and made the present invention.

That is, the gist of the present invention is to easily form a specialshape, for example, a shape having a high aspect ratio portion byforming a depression in a substrate to make a first original plate,transferring the pattern of the first original plate to make a secondoriginal plate having a protrusion corresponding to the depression, andmachining the protrusion of the second original plate to make a die.

Embodiments of the present invention will now be described withreference to the accompanying drawings in detail. The method formanufacturing a die according to the present invention includes thesteps of patterning a substrate by photolithography to make a firstoriginal plate, transferring the pattern of the first original plate tomake a second original plate, and machining the second original plate tomake a die.

The method according to the present invention makes it possible tomachine a fine structure that cannot be processed with an ordinarycutting tool 1 (whose tip width is normally 100 μm or more) used formachining and shown in FIG. 1. That is, it is impossible to finelyprocess (for example, to form fine depressions and/or protrusions in)tapered surfaces 3 a and a bottom surface 3 b of a depression 3 formedin a substrate 2 shown in FIG. 2 by machining using the cutting tool 1shown in FIG. 1. The method according to the present invention makes itpossible to make a substrate 2 whose tapered surfaces 3 a and bottomsurface 3 b in a depression 3 are finely processed.

In the method according to the present invention, a depression 4 isformed in a substrate 2 to make a first original plate as shown in FIG.3 (a), the pattern (depression 4) of the first original plate istransferred to make a second original plate 5 having a protrusion 5 acorresponding to the depression 4 as shown in FIG. 3 (b), and theprotrusion 5 a of the second original plate 5 is machined to formtapered surfaces 5 b and a top surface 5 c in the protrusion 5 a asshown in FIG. 3 (c). Further, the tapered surfaces 5 b and the topsurface 5 c are finely processed. Since the machining is performed onthe protruding portion 5 a of the second original plate 5, the machiningcan be performed regardless of the size of the cutting tool 1. Bythereafter transferring the machined pattern (protrusion 5 a) of thesecond original plate 5 to make a third original plate, a substrate 2having the desired shape shown in FIG. 2 can be obtained.

The method according to the present invention will be described in moredetail. First, in the step of making the first original plate, thesubstrate is patterned by photolithography as shown in FIG. 4 (a). Aresist layer (not shown) is formed on a substrate 11. The resist layeris hardened by being irradiated with light through a mask having apredetermined pattern. Thereafter, the resist layer is developed to forma resist layer corresponding to the predetermined pattern on thesubstrate 11. The substrate 11 is etched using the patterned resistlayer as a mask. Thereafter, the resist layer remaining on the substrate11 is removed to form a pattern 11 a (depressed pattern in this case) onthe substrate 11. Not only the semiconductor technology, in whichtwo-dimensional fabrication is mainly performed, but also the MEMS(Micro ElectroMechanical System) technology, in which three-dimensionalfabrication is performed, is utilized for the photolithography.

A silicon substrate or a plastic substrate such as a resist layer or anacrylic substrate can be used as the substrate 11. Wet etching, dryetching, isotropic etching, or anisotropic etching can be used asetching. Various resists such as a negative resist or a positive resistcan be used as a resist forming the resist layer.

By forming the pattern 11 a in the substrate 11 by photolithography inthis way to make a first original plate 11, a fine shape or a shapehaving a high aspect ratio (shape having a relatively high aspect ratioof, for example, one or more on the order of magnitude of micrometers)can be easily formed in the first original plate.

Next, in the step of making the second original plate, the pattern 11 aof the first original plate is transferred as shown in FIG. 4 (b). Amethod including transferring a pattern to a metal layer or a plasticlayer using metal electroforming or plastic molding can be used as amethod for transferring the pattern of the first original plate. Forexample, by electroforming nickel on a silicon substrate or a plasticsubstrate that is a substrate 11 in which a pattern 11 a is formed asdescribed above, and peeling the silicon substrate from the nickel plateformed by electroforming, the pattern can be transferred to the nickelplate that is a transfer layer. Alternatively, by forming a siliconcarbide plate on a silicon substrate patterned as described above andthen dissolving the silicon substrate, the pattern can be transferred tothe silicon carbide plate. The detail of this method is disclosed inToru Itoh et al., “SILICON CARBIDE MICROFABRICATION BY SILICON LOSTMOLDING FOR GLASS PRESS MOLDS,” Technical Digest of Transducers 2003,2A2.4, pp. 254-257. The content of this document is included in thisspecification for reference.

By transferring the pattern 11 a of the first original plate in this wayto make a second original plate 12, the below-described machining can beperformed without limitation due to the size of the cutting tool. If,for example, a depressed shape having a high aspect ratio is formed inthe first original plate, the pattern 11 a is inverted by beingtransferred to the second original plate 12 and appears as a protrudingshape. Therefore, even if the size of the depression is small, it ispossible to machine the inverted protruding pattern 11 a.

Next, in the step of making a die, the second original plate is machinedas shown in FIG. 4 (c). As described above, if, for example, a depressedshape having a high aspect ratio is formed in the first original plate,it appears as a protruding pattern 12 b in the second original plate 12.Therefore, this protruding pattern 12 b can be easily machined. Thismakes it possible to form a tapered shape or a curved shape in thepattern 12 b of the second original plate 12 with a high degree ofaccuracy, for example, a high degree of accuracy of ± 1/100° or moreaccurate in taper angle. That is, a part 12 a of the pattern 12 a can beremoved with a high degree of accuracy. The term “machining” here refersto ordinary machining using a cutting tool.

After machined, the second original plate 12 can be used as a die. Byperforming molding with this die, a molding having a specially shapedportion, for example, a high aspect ratio portion can be obtained. Themachined second original plate 12 itself can also be used as a processedarticle (processed article having a high aspect ratio protrusion in thiscase). According to the above-described method, photolithography is usedfor forming, for example, a high aspect ratio portion in a finestructure, and machining is used for processing an arbitrary shape inthe fine structure with a high degree of accuracy. Therefore, a specialshape, for example, a shape having a high aspect ratio portion can beeasily formed. According to this method, a portion requiringhigh-accuracy processing is machined but the whole is not machined.Therefore, the manufacturing process time can be shortened.

It is possible to transfer the pattern 12 b of the second original plate12 to make a third original plate 13 as shown in FIG. 4 (d) and to usethe third original plate 13 as a die or a mother die of a die. That is,a die may be obtained by transferring the pattern 13 a to anothermaterial using this third original plate 13 as a mother die, or thethird original plate 13 may be used as a die. Since the pattern 12 b ofthe second original plate 12 machined with a high degree of accuracy istransferred to this third original plate 13, the third original plate 13can have an arbitrarily shaped portion, such as portion X in FIG. 4 (d),in its fine structure. That is, the third original plate 13 has apattern 13 a including a tapered surface 13 b and a bottom surface 13 cfinely processed with a high degree of accuracy, which cannot berealized by conventional arts. Therefore, by making a die using such athird original plate 13 as a mother die and performing molding with thedie, a molding having a specially shaped portion, for example, a highaspect ratio portion can be obtained.

Methods for transferring the pattern 12 b of the second original plate12 to the third original plate 13 include the following methods. Forexample, in the case where the second original plate 12 is a nickelplate, another nickel plate is formed by electroforming nickel directlyon the nickel plate or with a mold release layer therebetween, andthereafter the nickel plates are separated to transfer the pattern tothe nickel plate that is the third original plate. In this case, theliquid composition in nickel electroforming may be appropriately changedto change the hardness of the nickel plate to prevent burr formation inthe third original plate. In the case where the second original plate 12is a silicon carbide plate, another silicon carbide plate is formed onthe silicon carbide plate with a mold release layer therebetween, andthe mold release layer is selectively dissolved to transfer the patternto the silicon carbide plate that is the third original plate.

As described above, also in the case where the third original plate 13is used as a mother die, since the second original plate 12 is used, itis possible to obtain a die with which, for example, a stripe groove ora fine depression or protrusion can be formed, to an accuracy ofmachining, in a tapered surface 13 b or a bottom surface 13 c of a finestructure that cannot be processed by machining and that is smaller thanthe size of the cutting tool used for machining. As a result, it ispossible to significantly expand the limit of die processing.

The method for manufacturing a die of the present invention can beapplied, for example, to the manufacture of a die of a microchannel or amicrolens array. FIG. 5 (a) illustrates a microchannel obtained by amethod for manufacturing a die according to an embodiment of the presentinvention. FIG. 5 (b) is an enlarged view showing a protruding part in(a).

The microchannel 22 shown in FIG. 5 (a) is about 10 μm in width andabout 20 μm in depth and is formed in a substrate 21. A plurality ofprotrusions 22 a are provided in this microchannel 22. In addition,shallow bottom surfaces 22 b and tapered surfaces 22 c are formed inthis microchannel 22. Such a microchannel 22 having the protrusions 22a, shallow bottom surfaces 22 b, and tapered surfaces 22 c cannot beformed by machining. As for photolithography, the taper angle θ shown inFIG. 5 (b) cannot be freely set. In the case where the microchannel 22shown in FIG. 5 is obtained in the substrate 21 by the method of thepresent invention, a groove corresponding to the microchannel 22 isformed by photolithography in a substrate that is a first originalplate, and the pattern is transferred to a second original plate. Atthis time, the groove portion corresponding to the microchannel 22appears as a protrusion. In this protrusion, depressions correspondingto the protrusions 22 a are formed by machining. By performing moldingusing the machined second original plate as a die and using the materialof the substrate 21, a substrate 21 having a microchannel 22 can beobtained.

In the case where a microlens array is obtained by the method of thepresent invention, depressions corresponding to a plurality of lensesare formed by photolithography in a substrate that is a first originalplate, and the pattern is transferred to a second original plate. Atthis time, the depressions corresponding to the lenses appear asprotrusions. Finish processing (mirror-like finishing) of theseprotrusions is performed by machining. By performing molding using themachined second original plate as a die and using the material of thelens array, a microlens array can be obtained. When the depressionscorresponding to the lenses are formed by photolithography, the amountof light (light exposure) to which the photosensitive resin (resist) isexposed is changed depending on place. This makes the thickness of thephotosensitive resin after development different depending on placeaccording to the light exposure, thereby forming curved surfaces in thedepressions corresponding to the lenses.

The present invention is not limited to the above-described embodiments,and various changes can be made therein. For example, the presentinvention is not limited to the sizes, numerical values, and materialsdescribed in the above-described embodiments. Although the method of thepresent invention is applied to a microchannel and a microlens array inthe above-described embodiments, the present invention is not limited tothis. The present invention can be applied to forming various shapesthat cannot be formed by photolithography alone or machining alone, forexample, a lens, a Fresnel lens, a reflecting mirror, or a groove for anoptical fiber, and combination of these, and combination of these and amicrochannel and/or a microlens array. Various other changes can be madewithout departing from the scope of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view showing a cutting tool used for machining.

FIG. 2 illustrates a shape obtained by a method for manufacturing a dieaccording to the present invention.

FIGS. 3 (a) to 3 (c) illustrate a method for manufacturing a dieaccording to an embodiment of the present invention.

FIGS. 4 (a) to 4 (d) illustrate a method for manufacturing a dieaccording to an embodiment of the present invention.

FIG. 5 (a) illustrates a microchannel obtained by a method formanufacturing a die according to an embodiment of the present invention.FIG. 5 (b) is an enlarged view showing a protrusion in FIG. 5 (a).

REFERENCE NUMERALS

-   -   1 cutting tool    -   2, 11 substrate (first original plate)    -   3, 4 depression    -   3 a, 5 b, 13 b, 22 c tapered surface    -   3 b, 13 c, 22 b bottom surface    -   5, 12 second original plate    -   5 a protrusion    -   5 c top surface    -   11 a, 12 b, 13 a pattern    -   13 third original plate    -   21 substrate    -   22 microchannel    -   22 a protrusion

1. A method for manufacturing a die, comprising the steps of: patterninga substrate by photolithography to make a first original plate;transferring the pattern of the first original plate to make a secondoriginal plate; and machining the second original plate to make a die.2. A method for manufacturing a die, comprising the steps of: forming adepression in a substrate to make a first original plate; transferringthe pattern of the first original plate to make a second original platehaving a protrusion corresponding to the depression; and machining theprotrusion of the second original plate to make a die.
 3. The method formanufacturing a die according to claim 1, further comprising the step oftransferring the pattern that the die has to make a third originalplate, wherein the third original plate is used as a die or a mother dieof a die.
 4. The method for manufacturing a die according to claim 2,further comprising the step of transferring the pattern that the die hasto make a third original plate, wherein the third original plate is usedas a die or a mother die of a die.
 5. A molding molded using a die, thedie being obtained by the steps of: patterning a substrate byphotolithography to make a first original plate; transferring thepattern of the first original plate to make a second original plate; andmachining the second original plate to make a die.
 6. A molding moldedusing a die, the die being obtained by the steps of: forming adepression in a substrate to make a first original plate; transferringthe pattern of the first original plate to make a second original platehaving a protrusion corresponding to the depression; and machining theprotrusion of the second original plate to make a die.
 7. The moldingaccording to claim 5, including a relatively high aspect ratio portion.8. The molding according to claim 6, including a relatively high aspectratio portion.
 9. The molding according to claim 5, including at leastone selected from a group consisting of a microchannel, a microlensarray, a lens, a Fresnel lens, a reflecting mirror, and a groove for anoptical fiber.
 10. The molding according to claim 6, including at leastone selected from a group consisting of a microchannel, a microlensarray, a lens, a Fresnel lens, a reflecting mirror, and a groove for anoptical fiber.